I just completed a short online course about essential oils and would like to share a warning about essential oils and cats. NEVER use any type of essential oil directly on a cat, not even blended in a carrier oil. They are way too strong for cats and are actually toxic. Not the same as other mammals, like dogs and horses, cats do not have the type of liver enzymes to break them down and get them out of their systems and essential oils could literally poison your cat to the point of death. It may be possible to use hydrosols, the byproduct of the steam distillation process of certain plants used to make essential oils, they are considerably weaker. But please make sure you know what you are doing and using on your cats. Once their liver is severely affected it may never be normal again. They cannot process essential oils just like they cannot process certain chemicals, that may be present in your cleaning products. I've seen several posts here, even if old, where the question was asked maybe a bit too late. Flower essences and Bach Flower Rescue Remedy are not the same as essential oils, but again make sure to respect your kitty's body, nose and metabolism. Maybe even take a look at cleaners you are using, citrus and herbal based cleaners while natural, can really be aggravating to your cat and his nose and paws are much closer to the floor you just cleaned. Don't use them to keep the litter box smelling good. If you want to use a diffuser for yourself, make sure to keep kitty out of the room for a few hours after it has finished. Never keep him enclosed in a room with a diffuser going. I'm sure someone will know the specific essential oils that could be extremely detrimental to cats, but know that generally speaking all essential oils are too strong and down right toxic for cats.